Compute values in vector with NumPy

Question

I use NumPy.

I have defined a vector x with NumPy and other variables with numerical values.

I will return a vector y of same length as x but the values y[i] in this vector y need to be computed from different formulas depending on the corresponding x[i].

Can I with NumPy do something smart or do I have to iterate through the vector x and for each element in x determine if x[i] is either greater than or less than a specific value and determine which formula to use for the specific element?

I guess I could do something like

y[x > a] = 2*x+7
y[x <= a] = 3*x+9
return y

jwilner · Accepted Answer · 2015-04-26 15:23:17Z

6

Check out np.where http://docs.scipy.org/doc/numpy/reference/generated/numpy.where.html.

y = np.where(x > a, 2 * x + 7, 3 * x + 9)

answered Apr 26, 2015 at 15:23

jwilner

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